Near-surface soil carbon, carbon/nitrogen ratio,and tree species are tightly linked across northeastern United States watersheds
Forest Science. 57(6): 460-469.
Forest soils hold large stores of carbon, with the highest concentrations in the surface horizons. In these horizons, both the total C mass and the C/N ratio may respond more rapidly to changes in tree species than lower horizons. We measured C and C/N ratios in the Oa or A horizon from 12 watersheds at 8 established forested research sites in the northeastern United States. The dominant tree species included Acer saccharum, Betula alleghaniensis, Fagus grandifolia, Picea rubens, and Tsuga canadensis. In 710 plots, both soil C (50-530g kg-1) and the C/N ratio (11.6-45.3) had a wide range. In all but the Cone Pond watershed, both N concentration and the C/N ratio were strongly related to C content. For these 11 watersheds, the average C/N ratio = 9.5 + 0.030 × C g kg-1 (R2 = 0.97, P < 0.001). Ratios at Cone Pond were much higher than would be predicted from this equation and charcoal was found in numerous samples, suggesting a source of recalcitrant C. Averaged by watershed, C concentration was also significantly related to C pools. The carbon concentration of the horizons sampled was negatively related to A. saccharum + B. alleghaniensis dominance and positively related to conifer + F. grandifolia dominance. The strong relationships between C, C/N ratio, and species suggest predictable patterns in C accumulation in near-surface soils.
Ross, Donald S.; Bailey, Scott W.; Lawrence, Gregory B.; Shanley, James B.; Fredriksen, Guinevere; Jamison, Austin E.; Brousseau,Patricia A. 2011. Near-surface soil carbon, carbon/nitrogen ratio,and tree species are tightly linked across northeastern United States watersheds. Forest Science. 57(6): 460-469.